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Chapter 4

PSY295 - Chapter 4 Notes (The Structure and Electrical Activity of Neurons).docx

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Katherine Krpan

PSY 295 CHAPTER 4: THE STRUCTURE AND ELECTRICAL ACTIVITY OF NEURONS Dendritic Spines branches and small protrusions that increase a dendrites surface area Axon Hillock a single axon that extends out of the cell body Axon Collaterals branches of an axon, which, usually emerge from at right angles Teleodendria smaller branches that are divided by the ends of axon collaterals Terminal Button (End Foot) knobs that are found on the ends of each teleodendrion Synapse the space between one axons end foot and the neighboring dendritic spine Neurotransmitter chemicals that carry a message across the synapse and increase electrical activity of the target Proteins complex organic compounds, including enzymes hormones and antibodies that form the principle components of a cell Nucleus an organelle that stores and copies a cells proteins (genes and chromosomes) Endoplasmic Reticulum (ER) folded layers of membrane where proteins are assembled Golgi Bodies membranous structure that packages protein molecules for transport Tubules tiny tubes that transport molecules and help give the cell its shape Microfilaments threadlike fibers that make up much of the cells skeleton Mitochondria structure that gathers, stores and releases energy Lysosomes sacs that contain enzymes designed to break down waste products Extracellular Fluid fluid that separates and cushions cells Intracellular Fluid fluid in which a cells internal structures are suspended Phospholipid Bilayer a membrane composed of a hydrophilic (polar) head and two hydrophobic tails Ions Charged particles with each end containing a positive or negative charge Chromosomes molecular complexes within the nucleus that house a cells genetic information Gene segment of DNA that encodes the synthesis for a particular type of protein molecule Amino Acids the building blocks of proteins Transcribe the process of copying a complementary strand of DNA/RNA Ribosomes complexes of enzymes and RNA that play a critical role in protein building Translation the reading of particular nucleotide bases into specific amino acid chains Messenger RNA (mRNA) the strand of DNA created from the template strand Polypeptide Chain a chain of amino acids Exocytosis a method used to excrete proteins from the cell Oscilloscope an instrument that turns electrical fluctuations into visible signals Diffusion the movement of molecules from an area of high concentration to an area of low concentration Concentration Gradient difference in the amount of a substance at different locations in a container Voltage Gradient the difference in charge between two connected regions that allow a flow of current Cations positively charged ions Anions negatively charged ions Resting Potential the electrical charge across a membrane that is maintained by differences in ion concentration Graded Potential slight, sudden changes in the voltage of an axons membrane Hyperpolarization stimulation that increases the relative membrane voltage Depolarization stimulation that decreases the relative membrane voltage Action Potential a brief but extremely large flip in the polarity of an axons membrane; lasting about 1 ms Threshold Potential the rapid change in polarity that occurs when electrical stimulation produces a large graded potential that causes depolarization in the cells membrane Absolutely Refractory the stimulation during the depolarizing or repolarizing phase of an action potential that limits the release of a new action potential Relatively Refractory when the action potential following another has a higher intensity Nerve Impulse the propagation of an action potential on the axon membrane Myelin Sheath insulation of axons produced by Schwann cells in the peripheral nervous system Nodes of Ranvier ends of an axon that are un-myelinated Saltatory Conduction the method in which action potentials jump from node to node Portrait Single-Cell Recording: Patients who suffer from epilepsy a disease which discharges abnormal electrical brain activity to interfere with normal movement, thought and consciousness were tested using wires inserted in the temporal lobes to determine the location of epileptic discharges.PSY 295 Once the source of epilepsy was recorded, surgeons were able to remove the abnormal brain tissues that produced each epileptic discharge. The wires used to record these activities contained eight smaller un-insulated tips that recording the electrical impulses. This procedure is known as single-cell-recording. Through similar experiments that recorded electrical discharges it was determined that particular neurons respond to well known objects, people, or even images of these things and the response properties are known as grandmother cells to indicate that particular neurons represent each particular object. Overview of a Neuron: Neurons are the information-conducting units of the nervous system that have special characteristics that allow it to send electrical impulses by using changes in chemical charges on its cell membrane. The most prominent feature of a neuron is its dendrites whose presence increases the cells surface. Further increases in the surface area can also be attributed to many small protrusions called dendritic spines which cover each dendrite branch. Each neuron may have 1-20 dendrites, each may have one or many branches and the spine on each branch may number in the thousands. The size of the surface area determines how much information a neuron can gather Each neuron has a single axon that extends out of the cell body known as the axon hillock little hill. Axons may also have branches axon collaterals, which emerge from right angles. Towards the end of an axon are a number of smaller branches called teleodendria and at the end of each teleodendria is a terminal button or end foot. Dendritic Spine Dendrite Axon (Axon Hillock) Axon Collateral Teleodendria Terminal Button
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